Chop onion and dice bacon.,Saute until golden.,Peel and grate potatoes.,Drain off liquid.,______,Add pepper, salt, onion, bacon and egg yolks.,Mix well. Stiffly beat egg whites and fold into the mixture.,Pour into well-greased roasting pan.,Bake at 350° for 1 1/2 hours. When done, slice into oblong pieces.,Serve with sauteed chopped bacon and onions, sour cream or both.